This invention relates to a method for providing termination members to flexible helical wire conduit and the termination members formed thereby. More specifically, it relates to the provision of flexible plastic termination members by injection molding.
Flexible conduit, typically comprising a plurality of concentric wire helices, is useful in a wide variety of applications. Such conduit, for example, can be used in conjunction with a movable inner element to transmit tensile compressive forces to locations remote from an operator. Such cable conduit constructions are commonly used to actuate automotive parking brakes and clutches and are used in other industrial, marine and aircraft remote control applications.
Because such conduits are typically made in continuous form of wound wire strands, particular care must be taken in their termination. Specifically, when the continuous cable is cut into segments of useful length, means must be provided to prevent the severed wires, usually steel, from springing outward and uncoiling before they are permanently secured. Heretofore, such conduits were typically secured prior to cutting by wrapping them with metal ribbon grooves to fit over the outer helical wire. After wrapping, the ribbon was sometimes swaged onto the conduit in order to form a rigid sleeve. In some instances a metal bushing-type anchorage fitting was crimped onto this shaped metal wrapping.
The difficulty with this swaged ribbon or crimped fitting approach is two-fold. First, it failed to obtain a good seal between the ribbon and the table. Despite the swaging or crimping operations, numerous small passages exist in the interstices of the elements. Consequently, moisture or even salt water can pass through these passages, penetrate to the interior of the conduit and corrode or freeze critical portions. Second, the swaged metal ribbon is relatively inflexible as compared to the conduit, thereby defining a point of vibration stress concentration when the swaged ribbon termination is secured by an external fitting. Consequently, the conduit is subject to premature failure at this point when subject to prolonged vibration and flexing as from a jouncing axle.